A skin diver inspects the submarine portion of a Wave Glider off the coast of Hawaii's Big Island. Notice the pivoting wings -- they provide about two knots of forward thrust for the entire apparatus. Photo: Brian Lam

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The Wave Glider Benjamin shows barnacle growth in areas not covered by a chlorine-based, anti-biofouling paint that's applied to most flat surfaces. The growth occurred during 120 days at sea during the California-to-Hawaii leg of the Pacific crossing. Photo: Brian Lam

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The Liquid Robotics team readies a glider for its next journey. Notice the relationship between the submarine and surface vessel. Image: Liquid Robotics

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The solar cells on the craft surface don't power forward movement. Rather, they power the sensors used for data acquisition. Image: Liquid Robotics

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Inside the Liquid Robotic R&D lab, new sensor payloads are installed on the gliders. This is also where the team tests its umbilical tethers -- connecting the floaters to the submarines -- for endurance. Photo: Brian Lam

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Can this Wave Glider survive the second leg of its Pacific journey? Time will tell. Image: Liquid Robotics

Robot Boats Survive Epic Voyage Across the Pacific — So Far

One of the Wave Gliders leaves Hawaii on the next leg of its epic ocean journey. Weather and wave sensors sit high on a pole above the vessel's surfboard-like surface. Image: Liquid Robotics

HAWAII — Twenty-two feet below the surface, the robot glider towed me slowly through clear Hawaiian seas. The day before, a similar glider named Benjamin had arrived in these same waters. Benjamin and three companion gliders had traveled all the way from San Francisco — more than 3,000 miles — powered by only the motion of ocean waves.

Before they left California, Liquid Robotics VP of Operations Graham Hine blessed the gliders by smashing a bottle of champagne on one of their frames, asking nature for assistance: “Neptune, god of the seas, and Aeolus, god of the winds, we ask for your blessings upon these vessels that are going to transit from here to parts formerly unexplored by this kind of robot.”

The gliders had endured an epic journey from California to Hawaii, but they were on a mere layover — they’re in the middle of an attempt to cross the entire Pacific. There’s a world record for “greatest distance by an autonomous wave-powered vehicle” at stake, and on Monday four of the gliders left Hawaii to resume their quest to cross the world’s largest body of water on mostly wave power. The next leg of their trip will take them some 5,000 more nautical miles to the coasts of Australia and Japan.

The Wave Gliders’ journey is more than just a title grab for a machine that was first created as a modest tool to track whale songs. And the journey is more than just an endurance test for the machines, which are capable swimmers.

For Liquid Robotics, the gliders’ long-term mission is to get as much data from the ocean as possible.

The Liquid Robotics Wave Gliders are taking divergent paths as they leave Hawaii for the Far East and Australia. Image: Google Maps

Over the course of their journey, Benjamin and its three Wave Glider companions — Piccard Maru, Fountaine Maru and Papa Mau, all named after famous ocean explorers and mariners — will capture about 2.25 million data points on the ocean’s physical characteristics. Liquid Robotics is making this data free to the public. In fact, the company is holding a contest to seek out novel proposals on how to use the data — the one with the most scientific potential wins. And the winner of the contest, called PacX, will receive six months of Wave Glider use as a prize. That, plus BP — yes, that BP — is throwing in a $50,000 research grant for the winner.

The first leg of the trip took Benjamin — named after Benjamin Franklin, who had studied the gulf stream — more than three months to complete. This is roughly 15 times longer than it would take a very fast sailboat.

The author swims with a Wave Glider off the coast of Hawaii. Photo: Brian Lam

I could see why.

To bystanders, a Liquid Robotics Wave Glider looks like a buoy, hardly moving at all. But I found that while swimming with a glider, if I looked down to adjust my dive mask for only a few seconds, it was already hastily swimming away.

The subtle, slow-but-steady, wave-powered drive of the Wave Glider is at the heart of what makes this technology so special. Machines that are passive enough to benefit from ocean power generally drift. But pilots can steer Wave Gliders using solar-powered electronics and satellite communication equipment, while all of the locomotion (the most energy-expensive element of any robotic vehicle) comes from the ocean itself. There’s no such thing as a perpetual motion machine, but these machines can nearly rove the oceans until they break.

Eric Brager, Test and Evaluation Manager at the Liquid Robotics R&D lab, says, “Even when it appears flat at sea, there’s enough ocean energy that the Wave Glider can still always be moving forward.”

The Wave Glider’s design is simple: A surfboard-sized float bobs on waves, big or small. That motion is transferred through a streamlined, 7-meter, rubber-and-steel cable to a submarine that cruises in the deeper, calmer waters. “In the rough open ocean, seven meters down, there’s virtually no up and down wave motion,” Brager says.

Indeed, oceanography teaches us that wave turbulence greatly diminishes below the surface of the water. For example, if you have a wave with a 20-foot length trough to trough, the waters underneath will be only 5 percent as turbulent 10 feet below the surface. The Wave Glider exploits this simple fact of physics to transform wave energy into forward motion.

A skin diver inspects the submarine portion of a Wave Glider off the coast of Hawaii's Big Island. Notice the pivoting wings -- they provide about two knots of forward thrust for the entire apparatus. Photo: Brian Lam

Here’s how it works: When the floating, surface-skimming portion of the Wave Glider attempts to force the submarine portion to flow with a wave, the sub is forced to carve upward through its relatively still waters. As this happens, an array of pivoting wings on the submarine lock into diagonal angles, transforming the bobbing wave motion into zig-zagging forward thrust at around 1 to 2 knots.

Because the solar array on top of the Wave Glider only has to power the rudder, satellite communications and whatever sensors are plugged into the modular payload, the glider, powered by the ocean’s endless undulations, can theoretically last much longer, and travel much farther, than any other ocean-going unmanned vehicle. That means a Wave Glider can go where a boat can — albeit slowly — but with the longevity of a buoy. This makes a Wave Glider an ideal platform for oceanic data collection.

During their pit stop in Hawaii, the gliders have been circling near Liquid Robotic’s R&D lab a few miles north of Kona on the Big Island. The lab, which sits on a dock, has on its wall the original prototype of the wave glider — it includes a wing-like whale tail and a surfboard. Another room is filled with crates containing Wave Gliders soon to be delivered into seas all over the world, and experimental next-generation gliders.

The building also houses a two-story-tall scaffolding set-up that simulates the strain of thousands of hours at sea on the Wave Glider’s mechanical drive components. This is where the engineers learned how to build an umbilical cord that can withstand hundreds of thousands of waves, big and small.

The lab is also where engineers apply wisdom gained from the California-to-Hawaii leg of the foursome’s journey. During their four-month voyage, the gliders encountered a storm with 26-foot waves and winds that maxed out the on-board sensors at 60 knots. A sailboat belonging to a Canadian family, only a few hundred miles away from the path of the gliders, needed to be rescued when their mast broke in the foul weather. But the Wave Gliders and their tethers held — just as they did in past storms.

Brager says the team wasn’t worried: “As fragile as they might look to some, I felt fairly confident that the things would stay together since we’ve been through storms like that before. We’ve done quite a bit of rough-water testing.”

Conventional wisdom tells us that larger boats survive much better in the open ocean, so there’s something to be said for an ocean craft that lets the water rush about it to do what it will. When explorer Thor Heyerthal took the Kon Tiki, a balsa raft of traditional Peruvian design, to sea in 1947, he observed that waves would come onto the deck, then harmlessly pass through the floor of the boat. This design stands in stark contrast to a modern hull, which would have taken on water and sunk without a bilge pump to swiftly remove the flood. And this speaks to the brilliance of the Wave Gliders: They don’t resist the flow of water, but rather exploit this very motion in the high seas.

Despite their seaworthy design, sometime during the first leg of their journey from San Francisco to Hawaii, half of the gliders suffered malfunctions that affected their ability to steer. Piccard, in fact, stopped turning without explanation. When the Liquid Robotics engineers recovered the glider, they found it had been scratched up all over. And then they found a tooth stuck in the umbilical cable.

The cause of failure? The glider was “seriously savaged by a major shark,” reads a statement on the PacX Liquid Robotics blog.

The Wave Glider Benjamin shows barnacle growth in areas not covered by a chlorine-based, anti-biofouling paint that's applied to most flat surfaces. The growth occurred during 120 days at sea during the California-to-Hawaii leg of the Pacific crossing. Photo: Brian Lam

Sharks have chewed on the Wave Gliders before. And, normally, sharks present far less of a threat to a Wave Glider than even a storm. Some researchers believe that sharks, using their electromagnetic sensing Ampullae of Lorenzini, sometimes become curious about metallic objects and may bite them. But the sharks normally bite the glider’s wings, doing no more harm than scratching off the anti-fouling paint that keeps the hull clean of microorganism growth so it may slipstream through the water. (When Benjamin was removed from the water, barnacle growth only occurred on the sections where this special paint had come off, or on areas left unpainted. This fouling is a major concern for the longevity of a glider at sea, as a dirty sub can lose up to half of its already meager speed.)

But in the case of Piccard, the glider suffered significant shark damage when the shark bit down on a particularly vulnerable section of the umbilical tether. The engineers took care to reinforce the vulnerable part of the cable before deploying it for the second leg of the Pacific crossing. They have yet to identify the kind of shark by the tooth fragment it left behind.

The gliders, moving slowly through the ocean for long stretches of time, also attract wildlife that mistake the vessels for flotsam. In the pelagic regions of the sea, often referred to as deserts, tiny fish will sometimes take refuge under the gliders, much as as they would under a floating palm leaf or tangle of kelp. Those fish attract predators, and some Liquid Robotics clients have been known to toss fishing lines near the gliders when they visit them for service.

As the Wave Gliders leave Hawaiian waters, they’ll be controlled from the company’s operations room in a non-descript Sunnyvale California conference room, where John Appelgren serves as the “admiral of the Wave Glider armada.” The control room is modest, looking less like a NASA mission control center and more like a conference room in the office of a generic business park. The table is covered with a few desktop computers.

Each screen displays software that looks like a slightly modified version of Google Earth. Each Wave Glider command takes an excruciating amount of time to execute compared to how one might pilot an aerial drone — which is fine, given the speed of these aquatic machines.

The Liquid Robotics team readies a glider for its next journey. Notice the relationship between the submarine and surface vessel. Image: Liquid Robotics

When I keyed up and hit send on a command to a Wave Glider as it sat in the Monterey Bay, it felt more like playing a board game than a video game. The pilots send the gliders commands, which sit in a queue until the glider polls the network connection via satellite. This happens every two to 15 minutes, depending on how much boat traffic is expected in the area. The more traffic an area has, the more often the pilots need to relay steering commands.

Although Liquid Robotics envisions more autonomous travel in the future — an inactive, grayed-out button reads “autopilot” on the software interface — the Wave Gliders are still piloted by humans. The majority of a pilot’s job is to steer the craft around larger vessels that are predicted to collide with the gliders in major shipping lanes, like the Gulf of Mexico.

Sometimes a potential collision is discovered in the middle of the night, and the pilot on call needs to scramble out of bed and reroute the glider out of harm’s way. None of the glider pilots I talked with had spent any time at sea as professional mariners. Nonetheless, they very quickly learn about navigating through the ocean while trying to pilot a vehicle with a two-knot maximum speed around much larger vessels that may easily surpass that.

“If there’s a hellish current coming,” Appelbaum says, “we could be cutting through the water rapidly, but be going backwards.”

The solar cells on the craft surface don't power forward movement. Rather, they power the sensors used for data acquisition. Image: Liquid Robotics

The pilots in the Wave Glider armada also need to manage the 655 watts of solar-charged batteries available to power the crafts’ electronics, sometimes cycling down certain gear when the juice runs low. (During Arctic winters, the gliders are capable of hibernating, and then rebooting days or weeks after gathering enough solar power.)

The sensors on the Wave Gliders can be customized to serve the needs of government, academic and industry clients that buy gliders for their own purposes. The gliders crossing the Pacific are loaded with a standardized payload that includes sensors for wind, wave height and direction, temperature, depth, and dissolved oxygen. There’s also a fluorometer for detecting crude oil and chlorophyll-A levels, which indicate the abundance of algal growth or petroleum in the water.

Regardless of whether the gliders succeed in their world record attempt, they’re still viable tools for ocean scientists, who are trying to get more data over a greater period of time and area. Biologists, for example, might use the oxygen and turbidity sensors to detect algae-rich areas that are becoming even richer with life. But the unique ability for the Wave Gliders to simultaneously sample air and water conditions makes them potentially invaluable tools for scientists studying the Earth’s oceans and weather patterns.

Brian Powell is an assistant professor of oceanography at the University of Hawaii. He uses a supercomputing cluster to simulate the ocean, just a few miles from beaches of Waikiki. His job is to take computer models of the ocean, and then rectify these models against real-world data. With these observations in hand, scientists can then revise and improve their modeling algorithms — which remain imperfect. “We have mathematical expressions for how fluids work as they apply to the oceans. But we can’t analytically solve these equations,” Powell says.

Especially interesting to Powell’s work is the ability of the Wave Gliders to measure water conditions such as salinity at the very same time they measure air conditions. This provides scientists with a much better understanding of the exchange between the ocean and our atmosphere. These ocean-air interactions affect coastal ocean and weather patterns, as well as our estimates of long-term climate shifts.

Inside the Liquid Robotic R&D lab, new sensor payloads are installed on the gliders. This is also where the team tests its umbilical tethers – connecting the floats to the submarines – for endurance. Photo: Brian Lam

“The wave glider is capable of monitoring that boundary between sunlight and the ocean, and how much rain is going into the ocean, which can help us build a more proper model,” Powell says. Indeed, an armada of Wave Gliders would give Powell more data to constrain his models, leading to modeling improvements all around.

Wave Gliders also have the potential to indirectly benefit scientists, acting as communications relays between undersea sensors and satellites.

Dr. Jonathan Berger, a geophysicist at the Scripps Institution of Oceanography at University of California San Diego, has a million-dollar National Science Foundation grant to explore the potential in using Wave Gliders to transmit real-time, deep-sea seismic sensor data to satellites, to shore. The current method for retrieving seismic data from these sensors is painfully archaic–they commission a boat to retrieve the sensors manually, and then place the sensors back under water. It can take days, if not weeks to plan such expeditions and, Doctor Berger adds, “is quite costly.”

Real-time undersea seismic sensors, operating from the floor of the ocean, could also work in concert with existing land-based sensors of the Global Seismographic Network in Project IDA (International Deployment of Accelerometers). The data could help build a real-time tsunami warning network, and provide a more complete global map of seismic activity. Graham Hines says this is one of many underwater projects that could benefit from the Wave Gliders’ long-term positions on the surface of the ocean. “Whenever you put something on the seafloor, it’s always a problem getting data to shore,” he says.

Can this Wave Glider survive the second leg of its Pacific journey? Time will tell. Image: Liquid Robotics

Wave Gliders are unique in some ways, but fit into a larger ecosystem of tools — including undersea drones, boats and buoys — that scientists may use to gather more data for less cost. That said, the Wave Glider is unique for its wave-powered drive and ability to stay at sea for very long time periods, under direct command and at low cost.

A boat may cost anywhere between “$10,000 to $100,000 a day to operate,” and depending on its depth, a buoy can cost “several hundred to a million dollars a year” says Hine. What’s more, boats can’t stay out in the ocean beyond the limitations of their fuel loads and crews, and buoys can’t move.

Wave Gliders cost around $200,000 each, but Liquid Robotics believes most customers will rent the vessels at a cost between $1,000 and $3,000 per day, sharing the gliders and their data, or even licensing historic data sets without buying any actual operating time. This could drive costs down even further.

The idea to move from a model of selling hardware to sharing and selling data was inspired by Silicon Valley’s modern culture of building data-centric products that scale through many users. To this extent, Liquid Robotics’ plan to share common resources is similar to renting server time from Amazon, rather buying and running one’s own web server.

Liquid Robotic’s current glider fleet is already doing specific missions for clients while simultaneously collecting data for a greater oceanic library. The company also has designs on a much larger data services fleet. Over the next 18 months, it plans to deploy hundreds of gliders positioned in Australia, the Gulf of Mexico, the Mediterranean, the Gulf of Maine, and other high-interest areas that should address the needs of companies and scientists.

I asked Hine if Liquid Robotics would create a larger Wave Glider for the sake of fitting more general-purpose sensors and solar power panels, but he wouldn’t directly comment on the future of Wave Gliders, only saying that “there’s some efficiency in making them larger.” He also added that Liquid Robotics is definitely interested in improving the capabilities of tomorrow’s Wave Gliders in terms of “Knots, watts and carrying capacity.”

That’s not a bad plan, if they’re going to try to capture an entire ocean’s worth of data.